Evaluation of heterologous ARS activity InS. cerevisiaeusing doned DNA fromS. pombe

Abstract

Cloned segments of Schizosaccbaromyce pombe genonic DNA were screened for ARS activity in the native host, S.pombe using high frequency transformation, phenotyplc instabillity and extrachromosomal maintenance of unrearranged plasmid sequences as criteria for ABS function. This analysis revealed 12 ARS elements in a total of 230 kb of chromosomal DNA, indicating an average frequency of one ARS every 19 kb of genomic DNA. We then used these clones to assess the reliability of the S. cerevisiae assay for detecting ARS elements in heterologous DNA. The results show that not only does the S.cereviaiae assay fail to detect a large proportion of true ARS elements but it also wrongly identifies a significant proportion of clones which did not display ARS activity in the native host. We would therefore recommend restraint when extrapolating from observed ARS function of heterologous DNA in S.cerevisiae to a presumed analogous role in the original host.